One. Scientific Foundations of Hollow Glass Microspheres 1.one Composition and Microstructure one.1.1 Chemical Composition: Borosilicate Dominance Hollow glass microspheres (HGMs) are mostly made up of borosilicate glass, a material renowned for its small thermal expansion coefficient and chemical inertness. The chemical make-up usually features silica (SiO₂, 50-90%), alumina (Al₂O₃, ... https://hackmd.io/@okok0972/rk1IrEjagl